The present invention relates to a process for the selective disproportionation reaction of olefins wherein an amine or a halogen compound is caused to be present during the disproportionation reaction of an olefin conducted in the presence of a carried tungsten oxide catalyst, thereby inhibiting the isomerization reaction of the olefin and increasing the conversion ratio for the disproportionation of the olefin.
It is widely known that various linear olefins are modified, or in other words, subjected to the so-called disproportionation reaction on a catalyst such as a supported tungsten oxide catalyst or a supported molybdenum catalyst, thereby to form a mixture of olefins which are larger and smaller in the molecular weight than the original olefins. However, a number of solid catalysts capable of promoting the disproportionation reaction of olefins are also catalytically active for the isomerization reaction of olefins where the double bond of the olefins is transferred. Thus, it is usual that when such solid catalyst is used for the disproportionation reaction of olefins, the isomerization reaction also takes place concurrently with the desired disproportionation reaction. For example, the disproportionation reaction of 1-butene affords only a mixture of ethylene and cis- and trans-5-hexene. In the case of using a solid catalyst such as tungsten oxide-silica, however, cis- and trans-2-butene are also formed from 1-butene by virtue of the isomerization activity of the catalyst and the disproportionation reaction takes place between the 2-butene and 1-butene, thus resulting in the formation of propylene and cis- and trans-2-pentene. Similarly, 1- and 2-hexenes are formed from 3-hexene and 1-pentene is formed from 2-pentene. These products give higher disproportionation products and the end products eventually become a mixture of very complicate olefins.
The co-disproportionation reaction of 2-butene and isobutene gives isoamylene and propylene. However, isomerization of double bond is caused by the same catalyst also in this case and, as the result, 1-butene is formed from 2-butene. Thus, the co-disproportionation reaction of 2-butene and 1-butene also takes place and the above mentioned complicate disproportionation proceeds parallelly to the production of linear pentenes. As the separation of the linear pentenes from isoamylene is difficult, the formation of the linear pentenes poses a serious problem.
As a result of many studies made for overcoming the above drawbacks in the disproportionation reaction of olefins, it has now been found that when an amine and/or a halogen compound is allowed to be coexistent with a carried tungsten oxide catalyst, the isomerization reaction of olefins is inhibited and the desired disproportionation of olefins is attained efficiently. The present invention has been accomplished on the basis of the above finding.